This invention relates to a system for quickly and automatically extracting and analysing residual solvents in material samples. Hereinbelow reference will be made particularly to preferred embodiments of the invention in which the samples are printed and/or laminated films, in general used as base supports for packing or packaging foodstuffs or pharmaceutical products, or liquid samples. Nevertheless, this is not to be understood as a limitation since the invention has several different applications, such as the analysis of residual monomers in polymers, the analysis of contaminated grounds, waters, and so on.
More particularly, the invention can be advantageously employed directly in the premises or plants where the materials for packing foodstuff and pharmaceutical products are being manufactured or printed and/or laminated.
As it is known the analyses of residual solvents present in printed and/or laminated packing materials, particularly those for packing foodstuffs and pharmaceutical products, are very important for the companies of this field.
According to a prior art technique, the analysis of residual solvents, for example in a film of plastic material, is carried out in laboratories by using an analytical system comprising a head-space sample container or thermal desorber, coupled to a gas chromatograph. During the manufacturing of the printed and/or laminated support or at the end of such process, a sample is collected and sent to the laboratory. The analysis results from the laboratory are available after times that are not compatible with the manufacturing schedules. Besides the high costs, the non-availability in real time of the analysis results often brings to discard large amounts of product and to reprocess the materials with additional costs.
This analysis is quite complex and requires high qualified technical personnel, and further has the following drawbacks:    the handling of the samples from the manufacturing plant to the analysis laboratory,    the use of test tubes, envelopes or other closed containers for transferring the samples to the laboratory with the associated risks of polluting the container content by the environment air, for example the air of the manufacturing plant when collecting the sample;    extremely complicated calibration procedures and frequent calibration controls, particularly for systems carrying out a subdivision or splattering of the sample;    long analysis times of the order of 45–60 minutes.
A further trouble of the known systems comes from the need to provide a pressure source and a gauge, which nevertheless does not allow a real knowledge of the pressure inside of the desorption chamber.
The scope of this invention is to eliminate the drawbacks and the limitations of the known systems, and more particularly to maintaining a higher pressure (overpressure) inside the desorption cell until a sample is introduced thereinto. By providing such overpressure or “washing” of the cell, it is possible to eliminate any pollutants coming from the desorption of a preceding sample and/or from the surrounding environment, whereby the system is suitable to be employed in the field still supplying reliable results. Preferably, the same fluid is used both as washing fluid and as fluid maintaining the high pressure, although this is not mandatory.
The above objects of this invention are achieved through a novel analyser for quickly analysing the residual solvent of a sample which analyser can be directly used in the sites where the packing article is being manufactured, printed and/or laminated.
The analyser according to the invention operates in a fully automatic manner and does not require highly trained personnel, reduces the handling of the samples to be analysed, and supplies results that are comparable with those obtainable in a laboratory by using the known procedures in times of the order of several minutes.
More particularly, for analysing printed and/or laminated packing articles, the system according to the invention can be advantageously located in the manufacturing premises, thus allowing for both the on-line analysing and the monitoring of the article being manufactured. As for what concerns the samples of packing materials, the invention allows to obtain the automatic analysis of solvent on both the sides of the sample, that is both on the outer side and on the inner side (that contacts the foodstuff or pharmaceutical product).
Moreover, the system according to the invention can operate on very small amounts of sample (the term “sample” being referred to the amount of the residual solvent) directly in the capillary column, thus eliminating sample splitting techniques that are subjected to introduce errors in the analysis.
According to the invention, these objects are achieved through a system for automatically extracting and analysing residual solvents in materials samples as described here.
Throughout all the Figures the same numerical references have been used to indicate equal or substantially similar parts.